Embodiments of the invention generally relate to electrical distribution devices, and more particularly to racking of electrical distribution devices, for example, circuit breakers.
Conventional electrical distribution equipment generally includes one or more circuit breakers, and often includes a plurality of circuit breakers housed in drawout units in switchgear housings and other electrical equipment. Periodically, the circuit breaker drawout units require removal to facilitate maintenance and or replacement of the associated switching devices. Similarly, additional switching devices may be placed within the drawout units. In order to facilitate placement of additional devices and/or removal of existing devices, the circuit breaker is “racked in” or “racked out,” respectively.
In general, a typical circuit breaker may be connected to the external power source through disconnects termed primary disconnects. The primary disconnects aid in connecting the circuit breaker to external power. The primary disconnects further aid the circuit breaker in being disconnected from the external power for maintenance or test procedures. Primary disconnects may also be termed clusters
Typical circuit breakers have three positions. The first position is a “connected position” in which primary and secondary disconnects of the circuit breaker are connected to a circuit. The second position is a “disconnected position” in which the primary and secondary disconnects are disconnected. The third position is a “test position,” in which the primary disconnects are disconnected but the secondary disconnects are connected. The test position allows a user, for example, to check the functioning of secondary or control power. Breakers may be racked between these three positions. If racking in, the breaker is moved from the disconnected position, through the test position, into the connected position. If racking out, the breaker is moved from the connected position, through the test position, into the disconnected position.
A racking mechanism is included in conjunction with the circuit breaker, such as a racking shaft, that allows for rotation of the mechanism to move the circuit breaker into the connected position. Furthermore, if a plurality of circuit breakers are included in a drawout box, additional racking mechanisms are used. It follows that as the number of primary disconnects or clusters increases, the force required for circuit breaker insertion/removal increases substantially. Thus, if more circuit breakers, or even larger circuit breakers, with differing current limiting requirements and/or thermal requirements are necessary for an application, breaker insertion/removal may be hindered due to large racking forces.